Roll-up doors are commonly used to provide access to the cargo-carrying bodies of trucks and trailers. They are also used on static structures, such as garage and warehouse doors and the like.
Roll-up door lock mechanisms have been in common use for many years.
Early forms of such lock mechanisms had a latch cam pivotally mounted on the lowermost door panel, and arranged to selectively engage a catch pin located in the door sill. A handle was mounted on the pivotal axis of the latch cam, and could be manually moved between opened and closed positions. Hold-open and hold-closed keepers were provided on the latch plate to selectively hold the handle in the opened and closed positions, respectively. When the handle was in its closed position, the hold-closed keeper was adapted to receive a padlock so to prevent the door from being unintentionally opened.
In early forms, the latch cam was secured to the handle mechanism so that these two members rotated together about the pivotal axis. See, e.g., U.S. Pat. No. 3,642,314.
Later developments improved on this by allowing some relative movement between the latch cam and the handle mechanism. In some forms, the latch cam could move by gravity relative to the closed handle. See, e.g., U.S. Pat. No. 3,642,314, supra. This had the advantage of allowing the latch cam to more firmly engage the catch pin when the vehicle was traveling so as progressively move the latch cam under the catch pin and to prevent a “dancing door”.
Later improvements added a spring between the latch cam and the handle to bias the latch cam to move into ever-tighter engagement with the catch pin as the vehicle traveled down a highway. This improvement was described in Overhead Door Corp. v. Whiting Roll-up Door Mfg. Corp., 1981 WL 48559, 215 USPQ 428 (W.D.N.Y. 1981).
While such roll-up doors and lock mechanisms are well known and in common use today, the problem of theft via forcible entry has persisted. Often, trucks or trailers are parked in vulnerable out-of-the-way positions. In other cases, trailers are carried by trains which may sit in rail yards for extended periods, or may travel through remote areas. The continuing problem of cargo theft is documented and recorded in Lockridge, “Cargo Safe & Secure”, Heavy Duty Trucking (July, 2011).
To strengthen the lock mechanism against possible theft, others have proposed to provide various removable anti-theft shields on the door handle. See, e.g., U.S. Pats. No. 5,737,946 and 7,874,188, the disclosures of which are hereby incorporated by reference. However, these forms contemplated that the anti-theft devices could be slipped on or added to an existing door lock. The apparent intent here was that such shields could be retrofitted to existing locks.
The problem with this arrangement is that the driver might typically operate the lock mechanism in daily use. The latch shield, while having a laudable purpose, interferes with, and impedes, the free unencumbered operation of the lock mechanism. Hence, some drivers would unlock the mechanism and physically remove the anti-theft shield to it from being an obstruction to the free use of the lock. Common complaints of removable guards are that they become damaged, lost, stolen or simply forgotten.
It is appreciated that no device can prevent theft by damage to a lock mechanism. Rather, such anti-theft devices simply provide an additional obstruction to a would-be-thief. It is felt that delay in defeating a lock mechanism is an additional theft deterrent in and of itself.
Accordingly, it would generally desirable to provide an improved anti-theft or theft-resistant shield or guard that can be associated with a roll-up door lock mechanism and that is not readily removable, even by the driver of the vehicle.